Engine governors in conventional engine controllers typically receive a throttle command and cause a quantity of fuel to be delivered to a combustion chamber of an engine as a function of the throttle command. Most engine governors are configured to determine a quantity of fuel that will regulate either engine power or engine speed.
The vast majority of engine governors use the throttle command to control the power output of the engine. For example, depressing a throttle pedal fifty percent (50%) of its full range of travel results in a power production by the engine of fifty percent (50%) of its maximum power capability. Typically this type of engine governor is relatively easy to implement. Further, when a fuel governor that controls engine power is used on a on-highway truck, the engine governor usually produces smooth acceleration regardless of the load on the engine since the engine produces a constant torque (assuming the throttle command does not change). When an engine has a light load or no-load condition, however, these types of engine governors often will run up the engine speed to its maximum. This occurs because even a small throttle command, e.g., ten percent (10%), will cause the engine to produce a quantity of power in excess of what is required, thereby causing an acceleration of the engine.
Some engine governors use the throttle command to control the engine speed. For example, depressing the throttle pedal fifty percent (50%) of its full range of travel results in a desired engine speed of fifteen hundred (1500) revolutions per minute (“rpm's”). This type of engine governor avoids the run up problem mentioned above since engine speed is regulated, but has its own disadvantages. For example, when an on-highway truck using the engine governor that controls engine speed experiences a transmission upshift, the resulting change in engine speed will cause an undesired change in the engine output, since the governor will apply fuel to regain the engine speed lost during the upshift. This application of fuel results in an unfavorable “surge” of power on all upshifts.
Further, engine governors that control engine power are generally mutually exclusive with those that control engine speed. Typically the quantity of fuel needed at a given moment to control engine power is different than the quantity of fuel needed to control engine speed. Thus, a manufacturer of engine controls must choose between the two types of engine governors, including their inherent advantages and disadvantages.